1. Field of the Invention
The present invention relates to a module wiper device incorporated into a vehicle together with a wiper motor, a link mechanism, and the like, which are integrated with the module wiper device.
2. Description of the Related Art
Conventionally, there has been known a module wiper device which has a wiper motor, a link mechanism, and the like integrated therewith, to facilitate incorporation of the module wiper device into a vehicle body. The wiper device of this kind has an advantage in that not only it can be easily incorporated into the vehicle, but also the strength of the wiper device itself can be improved because the wiper device has an integrated structure using a bracket, and therefore, it has been frequently used recently.
However, since a bracket used in the module wiper device is integrally molded by aluminum die casting, the bracket entirely becomes larger and increases in weight. Further, there is a drawback in that a mold of a die casting machine for forming the bracket also becomes large and expensive.
Accordingly, as shown in FIG. 7, there has been proposed a structure in which pivot holders 1a, 1b are connected by a pipe frame 2, a small-size bracket 4 is fixed to an intermediate portion of the pipe frame 2, and a wiper motor 3 is fixed to and supported by the bracket 4, with the result that the bracket itself is made smaller, lightweight and inexpensive (for example, see Japanese Utility Model Application Laid-Open (JP-U) No. 1-171767).
With the above structure, when the small-size bracket 4 is fixed to and supported by the pipe frame 2 at a position substantially equally distant from the pivot holders 1a, 1b (L1=L2), the distance between the bracket 4 and each of the pivot holders 1a, 1b is relatively long. For this reason, the pipe frame 2 can bend and stress can be absorbed by the bending of the pipe frame 2 to a certain degree, even if reaction force of an unillustrated wiper blade wiping is transmitted to the wiper motor 3, the small-size bracket 4 and the pipe frame 2 via link rods 5, 6. On the other hand, when the small-size bracket 4 is fixed close to one pivot holder 1a owing to unavoidable circumstances in that an arrangement space within an engine room is small, the distance between the small-size bracket 4 and the pivot holder 1a closer thereto than the other becomes short, so that an amount by which the pipe frame 2 can bend decreases. As a result, stress concentrates in a portion of the pipe frame 2 between the pivot holder 1a and the bracket 4 so that a crack may be formed in the pipe frame 2 or the pivot holder 1a.
In order to solve the above-described problem, conventionally, there has existed a structure shown in FIG. 8. Namely, among pivot holders 1a, 1b fixed to a vehicle body, one pivot holder 1b is connected via the pipe frame 2 to the bracket 10, the bracket 10 is fixed to the vehicle body, another pivot holder 1a and the wiper motor 3 are fixed to and supported by the bracket 10, with the result that the strength of the pipe frame is compensated for by using a relatively large bracket 10 including the pivot holder 1a without using a short pipe frame and the rigidity of the module wiper device is thereby improved.
However, although the above structure shows an improvement in size, cost and weight as compared with the die casting bracket, the bracket 10 becomes relatively large depending upon a position where it is mounted to the frame 2. Accordingly, even in this case, the bracket 10 increases in cost and in weight and there still remains need for improvement.